HIV dementia has only rarely been reported from countries infected with clade C virus. Opportunistic infections of the nervous system, however, are a major cause of morbidity and mortality in these developing countries. For example, in India where there are nearly 5 million patients are infected with the virus, it was estimated that nearly 25% of patients have CNS manifestations, most of which are opportunistic infections. Since these infections are treatable, it is imperative to determine the long-term impact of these infections on the brain. Preliminary data shows that the inflammatory infiltrates associated with these infections have a large number of HIV infected macrophages. It remains unknown, however, if inflammatory infiltrates associated with the opportunistic infection may serve as a portal of entry for HIV and if the virus may then establish residence in the brain and then continue to evolve within the brain. The degree to which these strains may cause neuro-glial cell dysfunction remains unknown. Further it remains unknown if patients with meningeal infiltrates would be at similar risks as those with parenchymal infiltrates. A major limitation to studying these neuropathological consequences of HIV clade C virus infection is the lack of autopsy tissues from these countries. NIMHANS is a unique institution that has conducted autopsies on patients that have died of AIDS since 1990. To the best of our knowledge, this is the only source of well characterized brain tissue specimens from HIV infected patients in Asia and Africa. This represents an excellent opportunity to address questions about disease pathogenesis that could not have been done otherwise. We thus propose to, 1. To determine the extent of glial cell activation and neuronal injury in HIV infected patients with CNS toxoplasmosis or tuberculosis. 2. To identify and compare viral sequences from HIV infected cells in inflammatory infiltrates associated with CNS toxoplasmosis or tuberculosis. 3. To determine if brain derived sequences of env and tat in inflammatory infiltrates cause glial cell activation or neuronal injury in vitro. These goals will be accomplished through collaborative efforts between Johns Hopkins University and NIMHANS. An excellent working relationship has already been established between the two institutions over the last several years. We have also devised a plan for training and technology transfer for the NIMHANS investigators. PUBLIC HEALTH RELEVANCE: CNS opportunistic infections are the major cause of morbidity and mortality in HIV infected populations in the developing world, however, the long-term impact of these diseases on the brain of patients successfully treated for these infections remains unknown. Using a unique resource of human brain autopsy tissue from India and a combined histopathological, molecular and cellular approach we will determine the mechanism of viral entry into the brain in the setting of the opportunistic infection and will also determine the impact of these infections on uninfected brain cells. This information will be critical in developing guidelines for long-term management of HIV-infected patients with opportunistic infections.